Enyne Cyclizations

By: Josephine Nakhla, Aldrich ChemFiles2009, 9.2, 16.

Aldrich ChemFiles2009, 9.2, 16.

Echavarren and co-workers have also demonstrated the utility of Au-NHCs in the reactions of 1,6-enynes. They determined that the outcome of the cyclization of 1,6-enyne 1 (Scheme 1) was dependent on the ligand coordinated to the metal. When 2 was used in combination with AgSbF6, the major product resulted from 5-exodig cyclization to afford a cyclopropyl metal carbene species, which upon reaction with the nucleophile afforded the carbocyclic product (see previous section). On the other hand, when the carbene-based Au-complex was used, the cyclopropyl derivative was observed as the major product.1